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Background: Polyurethane foam is a sound-absorbing material. The affective factors of its sound absorption have not received much attention in Iran. Therefore, the present study was conducted with aim to investigate the effect of sample thickness, air gap thickness, and sound intensity on sound absorption rate of open cell polyurethane foam.Methods: To conduct this experiment, the impedance tube was built based on the standards, and the absorption coefficient of open cell polyurethane foam with thicknesses of 25 and 50 mm was measured. Then, both foam thicknesses were evaluated in the 6 different sound intensities of 70, 80, 90,100, 110, and 120 dB. Furthermore, the absorption coefficient of the 25 mm thick foam with 5.5 cm of air and the 50 mm thick foam with 3 cm air layer on one side of the samples were measured. Then, the absorption coefficient of 40 mm thick foam was measured with 1 cm air layer and 2 cm of foam on either side, and then, 1 cm air layer and 4 cm of foam on either side.Findings: The obtained accuracy and efficiency showed that the impedance tube can be used with a correlation coefficient of 0.98. The effect of sound intensity on sound absorption was not significant in either of the two thicknesses of polyurethane foam. The air layer on one side of the 25 and 50 mm thick foam increased the absorption in average and high frequency ranges. The absorption coefficient of 40 mm thick foam with 1 cm of air in the middle increased in all frequencies, and of the sample with 1 cm air on one side, increased in high frequencies compared to the 5 cm thick foam without an air layer.Conclusion: According to the results of this study, the sound absorption coefficient of the open cell polyurethane foam can be improved with a higher thickness and by inserting a layer of air at the end or in the middle of the absorbent material.